—
In this video Paul Andersen explains how chemicals can cause both chronic and acute diseases. A discussion of the five main types of toxins; neurotoxins, carcinogens, teratogens, endocrine disruptors, and allergens is including. The LD50 method of determining toxicity as well as a discussion of bioaccumulation and biomagnification is is included.
—
—
Transcript Provided by YouTube:
00:04
Hi. It’s Mr. Andersen and this is AP environmental science video 32. It is on the health impacts
00:09
of pollution. Way back in the 1930s, the Chisso Chemical Corporation built a factory in Minamata
00:15
which is way southwest Japan. It was located between the Minamata River and the Minamata
00:19
Bay. And they were producing chemicals like acetyl aldehyde, which is not inherently dangerous.
00:24
It is used as a precursor to make things like vinegar. But they were using an enzyme that
00:30
contained mercury. And as the pumped the pollution back into the bay that methyl mercury got
00:35
into the food supply. And it moved its way up the food chain to the point where people
00:39
were eating fish that contained mercury in it. They started to develop a disease called
00:44
the Minamata Disease. They did not know what really caused it and then they eventually
00:47
traced it back to this factory. Over 2000 people developed Minamata Disease over that
00:51
time. And so anything that negatively impacts human health is a disease. It could be a chronic
00:56
disease that takes a long time to develop. Or it could be acute. It develops very quickly.
01:00
It can be caused by many different things. Disease could be caused by pathogens, like
01:05
viruses and bacteria. An example could be the ebola outbreak in Western Africa. That
01:10
would be an acute disease that comes on very quickly and is caused by an ebola virus. Human
01:14
health disease can also be caused by our risks. Smoking for example leads to lung cancer.
01:20
But it can also be impacted by pollution, in other words chemicals that get into the
01:23
environment become toxins and then they affect us in a negative way. We classify these in
01:28
five different groups. There are the neurotoxins which attack the brain and the nervous system.
01:33
We have carcinogens which will lead to cancer. We have teratogens which affect the embryo.
01:38
We have then endocrine disruptors which impact the endocrine system, the hormones in our
01:43
body. And then finally we have allergens which do not affect everyone. Now we use chemicals
01:48
in our body. So lots of time we have to figure out what is the safe dose of a chemical. And
01:54
so we use a test called the LD50. And I will walk you through that. The problem with a
01:58
lot of these chemical is they bioaccumulate. They are picked up by living systems and then
02:03
as they move up the food chain they biomagnify. And so we ban a lot of chemicals. The Stockholm
02:10
Convention was a convention to ban 12, they called them the dirty dozen, 12 endocrine
02:14
disruptors. And I think they have added another 9 since then. And so disease can be caused
02:20
by pathogens, but they can be acute. They come on very very quickly, like this outbreak
02:25
of ebola recently. But most of the diseases that impact humans, so this is a list of the
02:29
largest diseases in humanity, are going to come on very slowly. They are going to be
02:34
chronic diseases of the upper respiratory track. You see we have heart disease, stroke,
02:39
things like that that are killing most of the people on our planet. Health risks are
02:43
changing over time. So it used to be that the traditional risks were things like undernutrition,
02:50
bad air pollution inside, poor sanitation. But you can see over time we are shifting
02:55
towards more modern risks, smoking for example, obesity, inactivity, urban air quality. These
03:03
are becoming the risks of the modern world. And a lot of those risks are one that we take
03:07
on our own. So if we are looking at lung cancer deaths for example, most of those are formed
03:12
from smoking, not caused by air pollution. But this video is mostly about pollution.
03:17
It is about toxicology. It is about the harmful chemicals that can affect humans. And we break
03:22
those into five categories. The neurotoxins, so the methyl mercury in Minamata Disease
03:27
would be an example of that. Lead is a great example of a neurotoxin. So it is actually
03:32
damaging parts of the brain, especially the highlighted portions here in the prefrontal
03:37
cortex. So as this person right here is recycling batteries, that lead, they are being exposed
03:42
to lead, and that is going to be a neurotoxin. We also have carcinogens. These are chemicals
03:46
that can lead to cancer. A famous one would be asbestos which was used way back in the
03:51
1950s as an insulator. But now causes diseases like lung cancer and mesothelioma, which is
03:57
rare form of cancer caused by asbestos. We also have teratogens. These are going to be
04:02
chemicals that affect us before we are born. And so a famous example is thalidomide. It
04:07
was given to women and what it does is it decreases morning sickness. But what you got
04:11
were these awful birth defects, since it is a teratogen. Another example of that could
04:16
be alcohol. It causes fetal alcohol syndrome. We have endocrine disruptors. And so the way
04:21
that our cells communicate is through hormones. So it will dock with a receptor on our cell
04:25
and then there is a message that is sent into the cell. The way that endocrine disruptors
04:30
work is they either block that receptor, so the hormone cannot dock or they can imitate
04:36
the hormone itself. That is what DDT does. And the Stockholm convention was a number
04:40
of different countries that go together to ban the use these dirty dozen these 12 endocrine
04:45
disruptors. And then finally we have allergens. These are going to be chemicals that affect
04:49
each of us in a different way. And so this person is taking an allergy test where they
04:53
are exposed to all of these different chemicals and they are seeing where the response is.
04:57
And this can be deadly. If you think about a peanut allergy can lead to anaphylaxis.
05:00
And so you have to kind of know what chemicals you are susceptible to. Now almost all chemicals
05:06
on the planet can be a toxin if we get them in large enough amounts. And so what is the
05:10
safe amount of coffee for example that I can drink. Well we use a test called the lethal
05:15
dose or LD50 test. And a lot of this unfortunately is done on animals. What you do is you take
05:20
a new chemical and you apply larger doses to a set of mice for example. So the first
05:26
group is given very low amounts, low dosage. And then those at the end are given a high
05:31
dosage. And what you are looking at is mortality rate. So those that got a low dose, the percent
05:37
that died is almost nil. But those who got a high dose, 100% mortality. So to calculate
05:42
the LD50 what you do is you look for the point at which that graph crosses 50 percent mortality.
05:48
And so we could say it is at 3.8 milligrams per kilogram. You then divide that by 10 and
05:54
that is going to be your LD50 for mice. And so it would be 0.38 milligrams per kilogram.
05:59
That is going to be the safe dose. If we see where that is on the graph, it is going to
06:02
be way down here. Now the LD 50 then, to extrapolate that for humans, what we will do is we divide
06:08
it by 10 again, because there may be different susceptibility in humans and mice. And then
06:13
we will divide it by 10 again, just to be safe. And so the LD50 in humans would be 0.0038
06:20
milligrams per kilogram. Now the problem with a lot of these chemicals is they bioaccumulate.
06:25
So that methyl mercury that was pumped into Minamata Bay was picked up by phytoplankton.
06:30
In other words as they were taking in water they were taking in some of those chemicals.
06:34
They do not kill those phytoplankton. But those phytoplankton are eaten by zooplankton
06:39
which are eaten by small fish. And as we move up the food chain the chemicals do not go
06:43
away. They bioaccumulate. And so over time they get to larger and larger doses. And so
06:48
the EPA put a list out of what fish are safe to eat in an area where methyl mercury may
06:53
be found. And so they said at the lower parts of the food chain, krill and maybe oysters
06:59
for example it is safe to eat an unlimited amount of these. But as we move up to tuna
07:04
and sharks you should minimize the amount that you are eating because there are going
07:08
to be larger loads of mercury. Did you learn the following? Could you pause the video at
07:11
this point and fill in the blanks? Let me do that for you. Human health can be impacted
07:16
by diseases which are chronic. It take a long time or acute. It can be caused by pathogens,
07:21
like viruses for example ebola virus or risks like smoking. But pollution is chemicals that
07:27
are toxic to us. We break those into five categories, neurotoxins, carcinogens, teratogens,
07:33
endocrine disruptors, remember we used the Stockholm Convention as a treaty to try to
07:38
stop using the dirty dozen of these endocrine disruptors. We have allergens which affect
07:43
each of us differently. The dose response we use is the LD50 test. And then the thing
07:48
that we have to be wary of in environments is bioaccumulation, biomagnification. That
07:53
is health impacts of pollution. And I hope that was helpful.
—
This post was previously published on YouTube.